The four primary topics of investigation in the proposal are the following: 1) to devise a method, using vital staining or autoradiographic techniques, to mark the structure of sensory receptors whose functional characteristics have been identified electrophysiologically; 2) to determine how the localized cortical potential that we have found to be evoked by peripheral skin cooling in the human is related to thermal sensation by (a) measuring stimulus response curves of the potential at different adapting temperatures, and comparing these measures with psychophysical estimates of magnitudes of thermal sensation at the same adapting temperatures; 3) to (a) measure warm and cool sensitivity in humans as a function of adapting temperature by signal detection methods, (b) obtain sensation magnitude estimates of warm and cool stimuli as a function of skin adapting temperature, rate of temperature change, and skin area stimulated, and (c) identify the necessary and sufficient conditions for confusion of quality of thermal sensations that occur when large temperature changes are applied to the skin; (4) to evaluate, in cats, the effects of ablations of regions of somatosensory cerebral cortex on thresholds and latencies to escape from heat in a shuttle box.